Italian physician Francesco Redi (1626–1697),

His hypothesis was supported when maggots developed in the uncovered jars, but no

maggots appeared in either the gauze-covered or the tightly sealed jars. He concluded that

maggots could only form when flies were allowed to lay eggs in the meat, and that the

maggots were the offspring of flies, not the product of spontaneous generation.

TLS Online TPP Program

#Id: 4009

#Unit 2. Cellular Organization

           

TLS Online TPP Program

#Id: 4011

#Unit 2. Cellular Organization

A surprising feature is the lack of conservation of sequence in MAR fragments. They are usually 70% A-T rich. cis-acting sites that regulate transcription are common, as are 5’ introns, and a recognition site for topoisomerase II is usually present in the MAR.

TLS Online TPP Program

#Id: 4016

#Unit 2. Cellular Organization

The nuclear matrix and chromosome scaffold consist of different proteins, although there are some common components. Topoisomerase II is a prominent component of the chromosome scaffold, and is a constituent of the nuclear matrix, suggesting that the control of topology is important in both cases.

SATB1, is a protein that appears to regulate the association of MARs with the matrix in order to regulate transcription of genes in the vicinity of the MAR.

TLS Online TPP Program

#Id: 4017

#Unit 2. Cellular Organization

Chromosomes occupy chromosome territories in the nucleus and are not entangled with each other.

Heterochromatic regions, silenced genes, and gene-sparse regions of chromosomes are typically localized to the nuclear periphery.

TLS Online TPP Program

#Id: 4020

#Unit 2. Cellular Organization

Local genome alteration, termed kataegis involves activation-induced deaminase (AID)

Chromothripsis entire chromosomes or large parts thereof are shattered (thripsis in Greek means “shattering”) and stitched together again in what appears to be a random manner, leading to dozens or sometimes even hundreds of rearrangements.

TLS Online TPP Program

#Id: 4021

#Unit 2. Cellular Organization

Active genes are often found at the borders of chromosome territories, and active genes from several chromosomes may cluster in inter-chromosomal territories that are enriched in transcription machinery.